This invention relates to sewage treatment using gravity media filters, and more particularly, to a process for minute dosing of such gravity media filters.
Sewage effluent can be treated by gravity media filters. Oxygen deprivation in the filter media is a common problem when treating waste water by gravity media filtration. Continuous availability of oxygen is necessary to remove pathogens, including viruses contained in the liquid effluent subjected to such filtration.
Clogging of the filter media by biological material can produce undesired oxygen deprivation. If the flow rate of effluent to the input side of the filter media is too high, the excess water produces saturated flow which can lead to oxygen deprivation.
Load rate is an important factor in the operation of gravity media filters. It is important to produce a reasonably practical load rate while maintaining continuous treatment of pathogens by available oxygen.
Briefly, one embodiment of the invention comprises a process for treating effluent in a gravity media filter in which incoming sewage is initially filtered in a pre-filter to produce a liquid effluent which is then subjected to further treatment. The liquid effluent from the pre-filter is pumped to a pulse-feeding device intermittently discharging the effluent in short volume-controlled pulses at preselected time intervals. The effluent from the pulse-feeding device is forward pulse-fed to an array of drip irrigation emitters spread out over a surface area of a gravity media filter for feeding small doses of the effluent to the surface area of the filter at a rate substantially less than a standard drip irrigation rate.
The invention provides continuous treatment by available oxygen by avoiding clogging of the drip emitters and buildup of biological matter in the filter media, while also maintaining a reasonably practical load rate.
These and other aspects of the invention will be more fully understood by referring to the following detailed description and the accompanying drawings.